Wireless communication, such as radio communication, may be arranged to occur between mobile units, such as cellular telephones, wireless-enabled laptops or wireless sensors or other radio-enabled mobile devices, and base stations. A telephone call, for example, may be placed from a smartphone, from where it may be routed via an air interface to a base station. From the base station, the call may be routed through a cellular core network to a call recipient. Alternatively, a smartphone may be arranged to access the Internet, for example, via the air interface to the base station, and from the base station directly to a data communication network whereby a core network is in this case not needed to access the Internet.
Mobile radio-enabled devices, such as suitably enabled cellular telephones, may be capable of communicating with each other directly or locally. Such communication may be known as device-to-device, or D2D, communication. Direct D2D communication may comprise that a first mobile transmits information encoded in a radio signal, and a second mobile receives the radio signal, wherein the radio signal isn't re-transmitted along the way. In other words, radio energy encoded with information transmitted from the first mobile is received in the second mobile. Local D2D communication may comprise that involved mobiles exchange information via a base station, wherein the base station doesn't forward the information to a core network node or a radio-access network controller node.
D2D communication may be useful, for example, when coverage of a mobile communication network is insufficient. As a yet further option, D2D communication may be used to offload communication between two nearby mobiles to D2D mode, so that resources of the mobile communication network may be used to serve more users and mobile device power consumption can be reduced.
Mobiles may be enabled to have more than one radio carrier active at a given time. For example, a mobile may receive data via a wireless local area network, WLAN, radio network while being engaged in a video call over a wideband code division multiple access, WCDMA, network. Likewise some mobiles may simultaneously have active a D2D connection with another mobile, and at least one connection to a wireless network, such as WLAN, WCDMA or long term evolution, LTE.